1. Field of the Invention
This invention relates to the optically active benzene derivatives represented by the general formula (I): ##STR2## (wherein X represents --COO--, --OCO--, CH.sub.2 O-- or --OCH.sub.2 --; A represents a hydrogen atom, a halogen atom or an alkyl or alkoxyl group having 1 to 20 carbon atoms; R represents an alkyl group having 1 to 20 carbon atoms; l and m each represents a number of 1 or 2, n represents a number of 0 or 1, but when is 0 the sum of l and m is 3 or less; and * indicates asymmetric carbon atom), a process for producing the same, liquid-crystalline substances containing said derivatives as active ingredient, and optical switching elements utilizing the liquid crystal compositions containing said liquid-crystalline substances.
The term "liquid-crystalline substances" is used in this specification to refer to the liquid-crystalline substances of the broad sense, including those which may not have been confirmed to take a liquid crystal phase per se but can be utilized effectively as a liquid crystal composition.